38 



The function of the frog is to break the jar by receiving, in 

 conjunction with the posterior wall, the impact of the foot on 

 coming to the ground, and also to prevent slipping, and to stimu- 

 late the capillary circulation. 



The lateral cartilages form an elastic wall to the sensitive foot, 

 and their movements, caused by lateral expansion and contrac- 

 tion of the plantar cushion, assist the venous circulation. When 

 weight comes on the foot, it is relieved by a yielding foot articu- 

 lation on elastic walls, bars, and frog, and through this the 

 plantar cushion. The elastic posterior wall is pressed outward 

 by the compressed india-rubber-like frog and plantar cushion, 

 and it slightly expands from the ground surface to the coronet. 



At the moment of expansion the bulbs of the heels of the foot 

 at the coronary edges sink under the body weight and come 

 nearer the ground, as a result of which the anterior coronary 

 edge retracts. 



The pedal bone slightly descends through its connection with 

 the sensitive laminae and presses the sole down with it, while the 

 wall of the foot diminishes in height under the compression to 

 which it is exposed. Under these conditions the blood pressure 

 in the veins of the foot increases and the blood vessels are emp- 

 tied. When the weight is removed from the foot the blood ves- 

 sels fill, the frog and the posterior walls contract, the bulbs of 

 the heel rise, and the foot becomes narrower from side to side; 

 at the same time the anterior edge of the coronet goes forward, 

 and the pedal bone and sole ascend. The object of this expan- 

 sion is to assist the venous circulation and counteract concussion. 



Shoeing is a necessary evil, but by remembering the functions 

 of the various parts of the foot the damage resulting may be 

 limited to a comparatively small amount. 



The following rules may serve as a guide for the shoeing of 

 healthy feet: 



1. The wall being the weight bearer it should be pared per- 

 fectly level to avoid placing extra tension on any of the ligaments, 

 thereby causing the foot to be placed out of its true position. 



2. Fitting the shoe accurately to the outline of the foot, not 

 altering the latter to fit the shoe. Rasping away the exterior of 

 the crust to fit the shoe not only renders the horn brittle but is 

 so much loss of bearing surface. 



